Biocidal cementitious structures and methods of preparing them



BIOCIDAL CEIVIENTITIOUS STRUCTURES AND METHODS OF PREPARING THEM Alexander Klein, Danville, Calif., assignor to Kalman Floor Company, Incorporated, New York, N. Y., a corporation of Delaware No Drawing. Application December 27, 1950, Serial No. 203,027

6 Claims. (Cl. 10615) This invention relates to disinfe tin and sterilization, and has for its general object the provision of novel and improved ways and means for providing lg iggid a l a nd bactericidal buildin materials, particularly those pr'dviding exposed 528mm wall portions of building structures, for example, structures to be used as hospitals, nurseries, or food manufacturing or processing establishments such as bakeries, dairies, or the like.

The health departments of most cities, and of other political sub-divisions, have set up rigid requirements regarding sanitation in buildings in which food is handled or processed and one of the more important regulations is that which requires that the walls and floors be washed down periodically with a biocidal solution of proper concentration and effectiveness.

There are certain quite obvious difficulties attendant upon such periodic washing or spraying. In addition to the labor and expense of these frequent applications, there is the danger of contamination of the food products or raw materials with the disinfecant used, and the necessity of shifting supplies and equipment about with consequent loss of time and delay in production.

In view of these premises, it has heretofore been proposed to incorporate in the cementitious wall construction or wall covering material, a d s infectant agent which it was hoped would provide a permanent isinfect-ant action. However, such prior proposals have contemplated the addition of relatively large percentages of the disinfectant (from 0.1% to 4.0% by Weight of cement) which not only adds to the expense of the preparation but also introduces the possibility of weakening or otherwise adversely affecting the concrete, plaster, stucco, or other wall material.

It is therefore an object of the present invention to provide a cementitious wall or floor mix containing very minute quantities of disinfecapt which cannot adversely afiect the material in any way and which will provide a persistent, continuous, and inexpensive means for permanently disinfecting the walls of sanitary structures when they are built.

More specifically, it is an object of the invention to Provide ge nenthsnncretastucc gl hgruopr e mixture containing as little as 0.0001 percent of disinfectant by weight of the cement used.

Another feature of the invention is the provision of a new biocidal or bactericidal cementitious mix containing precipitated getgll ig silygg and/or organic and inor- United States Patent ice ganic compounds of silver, preferably in the colloidal state.

Specific examples of the relatively water-insoluble agents which may be used in accordance with the invention are precipitated metallic silver; silver chloride; Silvol, a colloidal silver-alkaline protein compound containing about 20% silver; Neo-Silvol, a compound of Silvol containing about 18% to 22% colloidal silver iodide; and Collargol (Collargolum), a colloidal silver and silver oxide compound formed by reduction and stabilized by egg albumen, and containing approximately silver.

These materials are mixed with the topping mixtures, the concrete used in wall or floor constructions, the wall coating materials such as stucco, plaster, plaster board, or the like, or if preferred, they may be mixed with the Portland or hydraulic cement before the concrete or other mixes are prepared.

Tests have shown that concretes containing as little as 0.000l% of these disinfectant agents by weight of the cement are rendered efiectively germicidal over an extended period of time. The addition of as much as 0.0005 is extremely efiective and the cost still negligible; and as much as 0.005% by weight of the cement may be employed without deleterious effect on the strength and wearing properties of the building material.

Comparative tests of the eliectiveness of these agents and of the well-known ermicidal solution Roccal have been made and the results of some 0 ese experiments are set forth below. Roccal is widely employed in the periodic washing down of walls and'floors of hospitals and food processing establishments. This composition is used in the form of an aqueous solution and the active ingredient is understood by the applicant to be a high molecular alk ldim e thyl bengyl-an mgnium clikride lbenzalkanium chloride) The high molecular alkyl group consists of a mixture of alkyl radicals from Cal-I11 to CmHs'z as contained in the corresponding fatty acids of cocoanut oil. The phenol cocfiicient is stated to be 25 for E. zyphosa at 20 C. While Roccal is a highly efiective bacteriological agent for short periods following its application, it has been found that this compound, as well as other water-soluble agents, when incorporated in concrete is subject to the leaching action of repeated washings of the concrete surfaces and is therefore not a permanent bactericidal agent under conditions normally obtalning in buildings where the floors or walls are periodically washed.

These tests are described and some of the results. set forth below:

The test specimens were 6 square inch samples of a regular 1 inch thick floor topping which were cut from larger panels. The bactericidal compounds were added at the time of mixing. Two diiierent concentrations were used in the tests described, namely, 0.0005 by weight of the cement and the relatively low concentration of 0.000l% by weight of the cement. For control purposes, specimens were also made up to which no bactericidal addition was made.

The specimens were cured in fog to the age of three months. The testing procedure was as follows:

1. The test specimens were sterilized.

Comparative eflectiveness of bactericidal compounds incorporated in concrete [Specimens cured in fog for three months] Staphylococcus Aurcus Living Organisms Recovered Bactericidal Compound After Exposure Time of- Amount, percent by wt. of cement 60hr. 288hr.

10. 000 None None None None Neo Silvol- Collargolum Precipitated silver metal 24, 000 17. 400 None Cultures exposed at room temperatures.

1,520,000 organisms planted.

Culture area 2.27 sq. cm.

Organisms suspended in 0.85%

saline solution.

Bacteriological Test Conditions The tests on washed samples of concrete containing bactericidal agents are described as follows:

above, the concentration of bactericidal agents contained in the concrete was only one-fifth, or 0.0001 percent by weight of cement in the case of the silver salts and silver metal, and 0.01 percent by weight of cement in the case of the Roccal reagent.

The bacteria used in the tests on washed samples consisted in an initial concentration of 10,000,000 E. coli for each specimen. A nutrient, tryptose phosphate broth, was used to start the test, and additional nutrient added before each count. The results of counts are shown in the table below.

The order of efiectiveness of the various bactericides after an exposure time of seven days was found to be: 1) precipitated silver; (2) Neo Silvol; (3) Silvol; (4) Roccal; (5) Collargolum; and (6) untreated.

After seven days of exposure of the repeatedly washed specimens, the precipitated silver was approximately 250 times as efiective, and the Neo Silvol and Silvol were 8 or 9 times as eifective, as the Roccal, even though the original concentration of the Roccal was times as great as that of these other materials.

Further tests were made on specimens or test samples which were cured in the fog room for a period of 30 months. These samples were 2 inches by 2 inches and 1 inch thick and were representative of heavy-duty congwoor toppings commonly found in industrial plants.

The concrete-mix was composed of 1 part of cement to 3 parts of sand and fine ravel, to which thFr'were added the bactericidal a e ts 1n the percentages shown in the table e? The samples were stored in the fog room, so that their surfaces were continually moist, for a period of 30 months before the beginning of the bactericidal tests. These tests were made on the specimens without scrubbing them as in the case of the previously described test. After removal of the specimens from the fog room, they were sterilized 'by exposure to ultra violet Comparative efiectiveness of bactericidal compounds incorporated in concrete, using bacterial organism E. coli and tryptose phosphate nutrient broth [Washed specimens] Bacterial Compound Living Organisms Recovered Alter Exposure Time oi- Type i' om 24hr(1da) 72hr (ads hr peroen y ys by wt. of (7 days) cement None 10. 000,000 320, 000,000,000 800. 000, 000, 000 6, 400, 000, 000 0. 0001 10, 000, 000 72. 300,000,000 570. 000, 000, 000 42, 000, 000 Sil 01 0.0001 10,000,000 260. 000. 000,000 300, 000, 000,000 48, 000,000 Collargol 0. 0001 10, 000, 000 190, 000. 000, 000 260, 000, 000, 000 2, 600, 000, 000 Precipitated silver metaL. 0. 0001 10. 000, 000 52, 000,000,000 65. 000, 000, 000 1, 540, 000 Boccal Agpgitx. 10, 000, 000 16, 600, 000, 000 190, 000, 000, 000 380, 000, 000

Note:

weight of cement.

These samples were treated preliminary to tests of bactericidal efiectiveness, in such manner as to simulate the effects of weekly washing of a concrete floor over a light and then inoculated with 2 ml. of E. coli in a nutrient broth. The initial concentration of E. coli was 10,000,000. The specimens were thereafter placed in period of one year. As compared to samples described 7 an incubator at 37 C. and microscopic counts of living rial, water, and a biocidal ingredient selected from the organisms were made after 24, 72, and 168 hours. The

group consisting of silver and silver salts, said ingredient results are set forth in the following table:

Comparative efiectiveness of bactericidal compounds incorporated in concrete, using bacterial organism E. coli and tryptose phosphate nutrient broth [Specimens cured in fog for 30 months with no scrubbing] Bacterial Compound Living Organisms Recovered After Exposure Time oi '1 Among our 24hr (id 72hr (Bda l68hr y percen ay ys pa by wt. of (7 days) cement None .s 10, 000, 000 228, 000, 000, 000 73, 000, 000, 000 6, 030, 000, 000 N e Sllvol 0. 0001 10, 000, 80, 000, 000, 000 63, 000, 000, 000 630, 000, 000 Precipitated silver metal.. 0. 0001 10, 000, 000 115, 000, 000, 000 l, 400, 000, 000 650, 000, 000 Roccal i l 0. 01 10, 000, 000 173, 000, 000, 000 42, 000, 000, 000 6, 200, 000, 000

At 432 hr. (18 days) exposure there were no living organisms remaining on tericidal compound.

It will be observed that in the foregoing test, the Neo Silvol and the precipitated silver metal, even in the minute amounts of 0.0001 percent by weight of the cement, were highly effective in their bactericidal action. Although Roccal was employed in an amount 100 times as great as Neo Silvol or precipitated silver metal, the number of living organisms recovered from Roccal-treated specimens were not much different from the numbers recovered from the specimens containing no bactericide.

It is understood that as employed in the present specification and claims, the term walls is used in a generic sense and includes not only the side walls of enclosures, but the floors and ceilings as well; and may also be considered as including any fixtures or installations made of or coated with cementitious compositions.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

any specimen containing a bacbeing present in an amount from about 0.0001% to about 0.0005% by weight of said cementitious material.

3. The composition of claim 1 wherein said biocidal ingredient is precipitated silver.

4. The composition of claim 1 wherein said biocidal ingredient is a colloidal silver-alkaline protein compound containing about 20% silver.

5. The composition of claim 1 wherein said biocidal ingredient is a colloidal silver-alkaline protein compound containing about 20% silver, to which has been added from about 18% to 22% colloidal silver iodide.

6. The composition of claim 1 wherein said biocidal ingredient is a compound of colloidal silver and silver oxide stabilized by egg albumen.

References Cited in the file of this patent UNITED STATES PATENTS 1. A cementitious building material mix for wall constructions and wall coverings for sanitary enclosures and 1 13%;: 2 Ce g Z t e like which comprises an inorganic cementitious mate- 6 51 l g i 3' 927 rial, water, and a biocidal ingredient selected from the 1818184 f 1931 group consisting of silver and silver salts, said ingredient 200813l p 5 being present in an amount from about 0.0001% to 204O806 eta uy about 0.005% by weight of said cementitious material. 2072809 f fi {3:

2. A cementitious building material mix for wall con- 4 41 gg 'g j 1948 structions and wall coverings for sanitary enclo ures an 2,627,476 Hemdon Feb 3, 1953 the like which comprises an inorganic cementitious mate- 

1. A CEMENTITIOUS BUILDING MATERIAL MIX FOR WALL CONSTRUCTIONS AND WALL COVERINGS FOR SANITARY ENCLOSURES AND THE LIKE WHICH COMPRISES AN INORGANIC CEMETITOUS MATERIAL, WATER, AND A BIOCIDAL INGREDIENT SELECTED FROM THE GROUP CONSISTING OF SILVER AND SILVER SALTS, SAID INGREDIENT BEING PRESENT IN AN AMOUNT FROM ABOUT 0.0001% TO ABOUT 0.005% BY WEIGHT OF SAID CEMENTITIOUS MATERIAL. 